Figure 3

Monitoring GLUT1 levels in RBC membranes. (A) The increase in GLUT1 levels in membranes after the addition of varying concentrations of C-peptide in the presence or absence of both Zn²⁺ or albumin. All increases are reported relative to basal levels of the GLUT1 in control donor cells in an albumin-containing buffer (PSS). The increase in red circles is for RBCs with varying concentrations of C-peptide added in the presence of both PSS and Zn²⁺. Black circles show samples containing C-peptide in PSS alone (no Zn²⁺), whereas gray triangles represent samples containing Zn²⁺ alone in PSS (with no C-peptide). White circles represent samples containing C-peptide and Zn²⁺ in an albumin-free form of the PSS (AF-PSS), in other words no albumin was present. A relative increase in measurable RBC membrane GLUT1 is only measured in the presence of albumin/C-peptide/Zn²⁺ (n ≥ 5, error = SEM). (B) The increase in measurable membrane GLUT1 for RBCs obtained from healthy control donors and donors with T1D, all realtive to basal levels of GLUT1 determined in membranes of the T1D cells and in the presence (striped bars) and absence (gray bars) of albumin (n ≥ 7, error = SEM, **p < 0.05 to Control RBC, *p < 0.05 to T1D RBC, #p > 0.1 to Control RBC).